man-pages/man2/gethostname.2

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.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
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.\" Modified 1995-07-22 by Michael Chastain <mec@duracef.shout.net>:
.\" 'gethostname' is real system call on Linux/Alpha.
.\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 2000-06-04, 2001-12-15 by aeb
.\" Modified 2004-06-17 by mtk
.\"
.TH GETHOSTNAME 2 2004-06-17 "Linux 2.6.7" "Linux Programmer's Manual"
.SH NAME
gethostname, sethostname \- get/set host name
.SH SYNOPSIS
.B #include <unistd.h>
.sp
.BI "int gethostname(char *" name ", size_t " len );
.br
.BI "int sethostname(const char *" name ", size_t " len );
.SH DESCRIPTION
These functions are used to access or to change the host name of the
current processor.
The
.B gethostname()
function returns a NUL-terminated hostname (set earlier by
.BR sethostname() )
in the array \fIname\fP that has a length of \fIlen\fP bytes.
In case the NUL-terminated hostname does not fit, no error is
returned, but the hostname is truncated. It is unspecified
whether the truncated hostname will be NUL-terminated.
.SH "RETURN VALUE"
On success, zero is returned. On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EFAULT
.I name
is an invalid address.
.TP
.B EINVAL
.I len
is negative or, for
.BR sethostname ,
.I len
is larger than the maximum allowed size,
or, for
.BR gethostname
on Linux/i386,
.I len
is smaller than the actual size.
(In this last case glibc 2.1 uses ENAMETOOLONG.)
.TP
.B EPERM
For
.BR sethostname ,
the caller did not have the
.B CAP_SYS_ADMIN
capability.
.SH "CONFORMING TO"
SVr4, 4.4BSD (this function first appeared in 4.2BSD).
POSIX 1003.1-2001 specifies
.B gethostname
but not
.BR sethostname .
.SH BUGS
For many Linux kernel / libc combinations
.B gethostname
will return an error instead of returning a truncated hostname.
.SH NOTES
SUSv2 guarantees that `Host names are limited to 255 bytes'.
POSIX 1003.1-2001 guarantees that `Host names (not including
the terminating NUL) are limited to HOST_NAME_MAX bytes'.
.SH "SEE ALSO"
.BR getdomainname (2),
.BR setdomainname (2),
.BR uname (2)